Transferrin and TIBC

Transferrin or TiBC may be requested by your doctor if they have reasons to suspect you have abnormal levels of iron in your body – either too little (iron deficiency) or too much (iron overload).

Usually the doctor will request other related tests at the same time, such as the iron level in the blood and the level of ferritin a protein involved in iron storage.

Transferrin or TIBC measurements may be requested when it appears that you have too much or too little iron in your body.

Your doctor may suspect you have too little iron if you have anaemia, especially if the red blood cells are small and pale (microcytic and hypochromic).

Your doctor may suspect you have too much iron if you have a family history of iron overload haemochromatosis or evidence of organ damage which could be due to too much iron.

In iron deficiency the transferrin and TIBC may be high. This may seem odd, but remember that the TIBC and transferrin are not measuring the amount of iron in the blood but the ability of the blood to carry iron. It seems that when the body lacks iron, it 'turns up’ the production of the iron-binding protein transferrin.

However, other things can turn the production of transferrin 'up’ or 'down’ apart from iron deficiency. For example, in people with chronic inflammatory conditions the transferrin (and TIBC) tend to be low. In women on the oral contraceptive pill, transferrin tends to be high.

For these reasons, your doctor will usually request other related tests as well as TIBC or transferrin, such as ferritin, if they suspect iron deficiency.

In iron overload, the transferrin and TIBC level are most useful when used together with the blood iron level to calculate the 'transferrin saturation’. In iron overload the transferrin saturation is high.

A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.

Disease	Iron	Transferrin/TIBC	UIBC	%Transferrin  saturation	Ferritin
Iron deficiency	Low	High	High	Low	Low
Haemochromatosis	High	Low	Low	High	High
Chronic illness	Low	Low	Low / normal	Low	Normal / high
Haemolytic anaemia	High	Normal / low	Low / normal	High	High
Sideroblastic anaemia	Normal / high	Normal / low	Low / normal	High	High
Iron poisoning	High	Normal	Low	High	Normal

About Reference Intervals

TIBC and transferrin and the other tests commonly used to assess iron function can be difficult to interpret because they can be affected by so many things other than body iron levels. Your doctor will need to consider all these other things when interpreting the results. You must tell your doctor if you are taking iron supplements.

Yes, there are numerous other causes of anaemia, however iron deficiency is the most common. If iron tests rule out iron deficiency then another cause must be sought. See the article on anaemia.

Transferrin is a protein that may decrease during any inflammatory process and is referred to as a negative acute phase reactant. Chronic inflammation, infections and cancer may cause changes in transferrin levels.